Why do you fall asleep in class?
Many factors are in play when you feel like falling asleep in class. You have an internal body clock that regulates when you’re awake and when your body needs to sleep. This is your circadian rhythm.
A compound called adenosine also plays a role. The level of adenosine rises when you’re awake and continues to increase the longer you’re awake. This increasing level of adenosine signals a shift toward sleep. Your body breaks down adenosine when you finally go to sleep.
When you don’t get enough sleep, you accumulate a sleep debt. If your sleep debt gets too high, you might feel like falling asleep in class.